1. Field of the Invention
The present invention relates to an adhesion type denture adhesive having superior cleanability, which can be easily removed from an oral mucosa and a denture base for cleansing after the use.
2. Description of the Conventional Art
A denture adhesive is a material for making unfitted denture stable in a mouth and exhibits an effect for compensating occlusion or mastication to make a person easy to talk. Such a denture adhesive is classified in terms of composition into a so-called xe2x80x9cclose contact typexe2x80x9d denture adhesive containing a vinyl acetate resin as a main ingredient and xe2x80x9can adhesion typexe2x80x9d denture adhesive containing a water-soluble polymer having high adhesiveness, such as karaya gum and sodium carboxymethyl cellulose, as a main ingredient.
The close contact type denture adhesive is a denture adhesive that removes air between a denture base and an oral mucosa and vacuum adsorbs a denture on the mucosa surface, thereby stabilizing the denture due to its adhesive properties. In general, the close contact type denture adhesive is an elastic rubber-like paste containing a vinyl acetate resin as a main ingredient. Since this close contact type denture adhesive is insoluble in water, it has characteristics that it is possible to take out the denture from the mouth and wash it with water and that it can be used even in the case where a gap between the denture base and the oral mucosa is relatively large. Further, it can be easily separated from the oral mucosa. However, the close contact type denture adhesive has involved defects such that it has irritation on the oral mucosa due to an alcohol present as one ingredient therein and that the denture adhesive is liable to remain on the resin-made denture surface, whereby works for removing the denture adhesive from the denture base for cleansing after the use are very difficult.
On the other hand, the adhesion type denture adhesive is a denture adhesive containing a water-soluble polymer such as karaya gum and sodium carboxymethyl cellulose, as a main ingredient, in which the water-soluble polymer comes into contact with a saliva between the denture base and the oral mucosa and is swollen and dissolved therein, thereby exhibiting adhesiveness and making the denture stick to the oral mucosa for stabilization.
The adhesion type denture adhesive is further classified, depending on the shape, into a powdered form; a paste-like form prepared by mixing the water-soluble polymer powder with a mineral oil such as Vaseline and liquid paraffin, or an anhydrous polyhydric alcohol such as glycerin and polyethylene glycol; and a sheet-like form prepared by once dissolving the water-soluble polymer powder in a solvent and then drying it by lyophilization or the like.
The adhesion type denture adhesive in any form is superior in stabilization effect to the close contact type denture adhesive and has a characteristic such that it is less in a feeling of wrongness because it can be applied uniformly and thinly between the oral mucosa and the denture base. However, the adhesion type denture adhesive has involved defects such that, since the water-soluble polymer that has been swollen and dissolved in moisture is in a paste-like state, works for removing the denture adhesive stuck to the denture base or oral mucosa for cleansing after the use are difficult and that the denture adhesive attached on the denture base or mucosa surface cannot be easily removed.
An object of the present invention is to overcome the above-described defects of the denture adhesive of the conventional art and provide an adhesion type denture adhesive having superior cleanability while keeping a superior denture stabilization effect, which can be easily removed from a denture base and an oral mucosa for cleansing after the use.
We, the present inventors made extensive and intensive investigations in order to achieve the above-described object. As a result, it has been found that when suitable amounts of an alginate and calcium sulfate are mixed into an adhesion type denture adhesive containing a water-soluble polymer as a main ingredient, not only the resulting adhesion type denture adhesive has superior adhesiveness due to swelling and dissolution of the water-soluble polymer upon contact with moisture such a saliva, but also it becomes in a gel-like state due to a fact that a calcium alginate gel formed by the reaction of the alginate and calcium sulfate during the contact with moisture contains a paste of the water-soluble polymer, whereby it can be easily removed, together with the water-soluble polymer, from a denture base or an oral mucosa for cleansing after the use, leading to accomplishment of the invention.
Specifically, the denture adhesive according to the invention is a denture adhesive containing a water-soluble polymer as a main ingredient, and containing 0.5 to 60% by weight of an alginate and 0.1 to 20% by weight of calcium sulfate.
As the denture adhesive according to the present invention, any conventional denture adhesive that has hitherto been used can be used without particular restrictions so far as it contains a water-soluble polymer as a main ingredient and utilizes adhesiveness by swelling and dissolution of the water-soluble polymer. When suitable amounts of an alginate and calcium sulfate are mixed into this adhesion type denture adhesive, the resulting denture adhesive can be easily removed from a denture base and an oral mucosa for cleansing after the use, and consequently, it possesses superior cleanability.
Examples of the water-soluble polymer that has hitherto been used for the present invention include karaya gum, sodium carboxymethylcellulose, gum arabic, sodium polyacrylate, and a methoxy ethylene-maleic anhydride copolymer. In the invention, two or more of these water-soluble polymers can also be used at the same time.
Examples of the alginate that is used for the denture adhesive according to the present invention include sodium alginate, potassium alginate, ammonium alginate, and magnesium alginate. A suitable amount of the alginate to be mixed is 0.5 to 60% by weight, and preferably 5 to 30% by weight. When the amount of the alginate to be mixed is less than 0.5% by weight, the effect by a calcium alginate gel cannot be provided. On the other hand, when it exceeds 60% by weight, the operability during the use of the denture adhesive is deteriorated.
The higher a molecular weight of the alginate, the higher a gel strength of calcium alginate as formed, and hence, such is more suitable. Since it is difficult to define the molecular weight of the alginate, it is general to define the molecular weight in terms of a viscosity under prescribed conditions. Accordingly, it is preferred that the alginate used in the invention has a viscosity of 50 to 1,000 cP, and preferably 700 to 1,000 cP at 25xc2x0 C. in terms of 1% by weight aqueous solution.
Calcium sulfate that is used for the denture adhesive according to the invention may be in the form of either a dihydrate or a semi-hydrate. A suitable amount of calcium sulfate to be mixed is 0.1 to 20% by weight, and preferably 0.3 to 8% by weight. When the amount of calcium sulfate to be mixed is less than 0.1% by weight, the effect for gelling the alginate is not provided. On the other hand, when it exceeds 20% by weight, the fluidity of the denture adhesive during the use is deteriorated, so that the denture adhesive cannot be thinly applied in a gap between the denture base and the oral mucosa.
The denture adhesive according to the invention may be in any of a powder form, a paste-like form, or a sheet-like form, like the adhesion type denture adhesive of the conventional art. In the case where the denture adhesive according to the present invention is in a powder form, a water-soluble polymer powder, an alginate powder and a calcium sulfate powder are mixed and then provided. In this case, the denture adhesive powder is sprayed on a denture base that is moistened by water in advance, and an excess of the denture adhesive is shaken off, followed by inserting the denture into a mouth and providing it for the use.
In the case where the denture adhesive according to the present invention is in a paste-like form, the mixture in a powder form is mixed with a mineral oil such as Vaseline and liquid paraffin, or an anhydrous polyhydric alcohol such as glycerin and polyethylene glycol, in an amount of at most 60% by weight, and preferably 15 to 60% by weight, to prepare a paste. In comparison with the powered denture adhesive, the paste-like denture adhesive does not require a denture to be moistened with water in advance and is spread more uniformly and thinly on the denture base surface. Thus, the latter is superior in the operability.
In the case where the denture adhesive according to the invention is in a sheet-like form, the respective components including the water-soluble polymer, the alginate and the calcium sulfate are once mixed in a solvent and then dried by lyophilization or the like, to prepare a sheet. The sheet-like denture adhesive is moistened by water and laminated on the denture base surface to adjust the shape, followed by inserting the denture into a mouth and providing it for the use.
As a matter of course, the denture adhesive according to the present invention can be mixed with other optional components so far as the effects of the invention are not inhibited. Examples of such optional components that can be used in the present invention include a preservative, a pH adjustor, an enzyme, a pigment, and a fragrance or flavor.
The invention will be specifically described with reference to the following Examples, but it should not be construed that the invention is limited thereto. In each of the Examples and Comparative Examples, the alginate was designated with a viscosity at 25xc2x0 C. in terms of a 1% by weight aqueous solution.